A photographic roll film cartridge typically includes a flanged spool upon which is wound a long strip of backing paper to which has been attached on one side thereof a strip of light sensitive photographic film. The ends of the backing paper are positioned to extend beyond the ends of the film and constitute light protective leader and trailer strips for film which is interwound with the backing paper so that it separates adjacent revolutions of the film.
Roll film backing paper is paper which is attached to a roll of film. The purpose of the roll film backing paper is to provide an opaque back surface which acts as a lightlock for the film and to provide antistatic protection to the emulsion which is coated on the other side of the film. Typically roll film backing paper consists of a paper to which is laminated a plastic material containing carbon black particles. However, polymer backing papers used in the past have had a problem with adhesion of the carbon black and polymer blend to the paper. Prior art solutions to this adhesion problem include the use of adhesive copolymers and lamination. It would be desirable to have a backing paper which did not use adhesive copolymers or multiple laminations to provide adequate adhesion of the polymer blend to the backing paper.
U.S. Pat. No. 5,360,701 describes an antistatic backing paper for photographic roll film. This patent teaches that one can prepare an antistatic roll film backing paper for photographic roll film by applying a polyethylene layer to a paper substrate and then applying an opaque layer at a temperature high enough to bond to the polyethylene. The opaque layer consists of polyethylene and 7 to 10 weight percent mixture of conductive and nonconductive black particles. The mixture contains 20 to 80 weight percent conductive black particles. This patent also teaches that when the proportion of carbon black particles is more than 10 percent of the total weight of the polymer blend, the polyethylene melt cannot be readily extruded onto the paper base. Moreover, there is reduced adhesion of the polyethylene melt to the base.
U.S. Pat. No. 4,584,234 discloses a wrapping material for photographic materials produced by laminating layers on a paper support. The laminated layer includes a thermoplastic resin on one side of the paper support, the thermoplastic resin being a blend of high density polyethylene and low density polyethylene. The blend of polyethylene used in the examples has 5 weight percent carbon black.
U.S. Pat. No. 4,579,781 describes a material for packaging light-sensitive materials which consists of a laminate of a substrate, a polyethylene polymer layer which contains no light-shielding material and a laminate comprising a light-shielding material outside the polyethylene layer. Thus, this material is a composite laminate composed of a low density polyethylene film and a separate light-shielding layer.
There is a need for a polyethylene backing paper which has improved strength, friction properties and is easily manufactured. The present invention solves these problems by providing a single layer of polyethylene with conductive carbon black particles.